Interest in using cannabidiol for domestic animals has escalated with the legalization of marijuana in many states. Tarleton State University’s Equine Center, part of Texas A & M University, is evaluating the effects of non-psychoactive cannabidiol (CBD) on inflammation, stress and stereotypical negative behavior in horses. Horses in the trial are given CBD in oil or pellets, then heart rate and cortisol levels are measured along with observations of the horses for CBD effects on pain, lameness, and obsessive-compulsive behaviors.
In addition, the study examines how long CBD remains in a horse’s system as that information impacts a horse owner’s ability to comply with drug-free competition requirements. Results of this study are forthcoming in 2021.
Another pilot study is being conducted at Murray State University to examine the effects of CBD for behavior modification in horses [Jones, K.; Thomas, E.; Draeger, A.; and Porr, S. Evaluation of CBD Supplementation in the Horse].
An initial project looked at detection in blood of two horses given a single dose of 50 mg CBD in oil or pellets at 1 and 2 hours post administration. No CBD was detected in any of the blood analysis at the standard lower limit concentration of 1 ng/ml.
A second project over a 12-hour period evaluated pharmacokinetics with three groups of six horses each: a) single dose of 50 mg pellets; b) single dose of 100 mg pellets; c) single dose of 250 mg pellets. Blood samples were collected at pre-treatment, 30 minutes, and at 1, 2, 4, and 12 hours after administration. Peak concentration and clearance times mirrored results found in other species. The highest dose of 250 mg was consistently detected at 1 ng/ml. Liver enzymes changed but remained within normal levels, yet this needs further study.
The third project evaluates behavior and movement of 12 horses each in two groups: a) 100 mg pellets given daily for 12 weeks compared to controls given pellets without CBD. The study measures behavioral reactions to novel objects and impact of CBD on pain and performance related to flexion and movement evaluations. Blood is analyzed every two weeks over the 12 weeks of supplementation. This project is in process at the time of this writing.
Murray State University personnel initially concluded that the recommended small animal dose of CBD of 25-50 mg/day is too low for horses. Using higher doses, the low-end dose over time might accumulate in the tissues and after several weeks might modify adverse behaviors. Higher doses might achieve more immediate results to mitigate painful conditions such as osteoarthritis.